I havent disassembled a p31 before, but if it is like the p51, then you just have to remove the small cover of the sim and memory card slots, unscrew the screws you find there, then from there, run your thumb nail along the lengthof the phone in the tiny space between the two parts. I said your nail so you do not break the plastic or clips holding them, because, with your nails you have more control over the pressure you apply